South America

The most probable cause for the occurrence of this accident was the loss of situational awareness, caused mainly by the change of flight conditions under visual rules to flight under instrumental flight rules, due to the adverse weather conditions in which the descent phase began, so it is possible to establish the Human Factor as the cause of the accident and the Physical Factor as a contributor.

The following findings were identified:
- The LEFT MAIN LANDING GEAR ASSEMBLY (PN D23189000-19 and SN MN1700) collapsed, failing with 5,130 cycles after the last overhaul.
- A specific component (pin) of the assembly connecting the landing gear to the airframe, the AFT PIVOT PIN (P / N D61000, S / N 25), broke on account of fatigue, whose onset was facilitated by a machining process carried out in the pin section transition region.
- The ANAC-approved ATR72 Series Aircraft Maintenance Program of the TRIP Linhas Aéreas company read that the LEFT MAIN LANDING GEAR ASSEMBLY had to undergo overhaul every eight years or 18,000 cycles.
- On 27 February 2009, the PR-TTI landing gear was removed and, on 09 March 2009, was sent to be overhauled by the AV Indústria Aeronáutica Ltda. It had 31,684 cycles since new and 18,095 cycles since the last overhaul.
- AV Indústria Aeronáutica Ltda. was homologated for conducting such inspection, as specified in the List attached to the Addendum, Revision no. 11, dated 05 January 2009, and accepted by means of the Official Document no. 0173/2009-GGAC/SAR, issued by the Civil Aviation Authority.
- The AV Indústria Aeronáutica Ltda. company disassembled the legs of the landing gear, and outsourced some of the tasks for not possessing technical knowledge and/or appropriate machinery (necessary for the process of reconditioning the AFT PIVOT PIN (D61000 SN 25).
- Two of the three companies outsourced by AV Indústria Aeronáutica Ltda. were not homologated by the Civil Aviation Authority.
- The AV Indústria Aeronáutica Ltda. company conducted external audits of the three companies involved in the overhaul.
- The audits carried out by AV Indústria Aeronáutica Ltda. were not sufficient to identify that the contractors lacked qualified personnel, manuals and the machinery necessary to work with aeronautical products.
- The AV Indústria Aeronáutica Ltda. Technical Manager did not supervise the overhaul inspections and services performed by the contracted companies.
- The AFT PIVOT PIN (D61000 SN 25) is part of the assembly that connects the landing gear to the airframe.
- All revision tasks were described in the manuals of the manufacturer.
- The AFT PIVOT PIN (D61000 SN 25) failure-analysis report stated that the PRTTI aircraft left main landing gear collapsed on account of fatigue, whose onset was facilitated by a machining process carried out in the section transition region of the pin.
- The manufacturer's maintenance manual did not refer to any machining work in that region of the pin.
- In only one stage of the pin reconditioning process was it possible to observe that a machining task was required, namely, the Grinding of chromium.
- The lack of capacitation and training of the subcontractors’ professionals for handling aircraft material hindered the execution of an efficient maintenance work as prescribed by the manufacturer's manual, culminating in inadequate machining during the maintenance process.
- The lack of an effective process of supervision, both on the part of TRIP Linhas Aéreas and on the part of the other contractors and subcontractors allowed the existing maintenance services’ latent failures not to be checked and corrected, in a way capable of subsidizing, in an adequate and safe manner, the execution of the landing gear maintenance service.
- The process of supervision of the TRIP Linhas Aéreas and the AV Indústria Aeronáutica Ltda. companies by the Civil Aviation Authority, prescribed by specific legislation in force, was not enough to mitigate the latent conditions present in the accident in question.
- According to the technical opinion issued by the DCTA, the AFT PIVOT PIN (D61000 and SN 25) presented fracture surfaces with ± 45º inclination, as well as a flat area with multiple initiations, indicative of a fracture mechanism related to fatigue. In examinations of the external surface of the pin, in a region close to the fatigue fracture, cracks were observed that had initiated from scratches created by an inadequate maintenance machining process. In the region where the overload-related fracture occurred, it was also possible to identify that the machining process had modified the profile of the part in the section transition region, by producing a depression. Thus, it can be said that the AFT PIVOT PIN (D61000 and SN 25) of the PR-TTI left main gear broke on account of fatigue, whose onset was facilitated by an inadequate machining process that had been performed in the section transition region of the pin.

The following findings were identified:
- Factors, such as obesity and sedentariness, associated with the high workload in the moments preceding the collision with the hill, may have contributed for the task demand to exceed the margins of safety, resulting in wrong decision-making by the pilot.
- Upon facing adverse meteorological conditions and being aware that aircraft which landed before him had reached better visibility in altitudes below 3,500 ft. on the final approach of the VOR procedure, the pilot may have increased his level of confidence in the situation, to the point of descending even further, without considering the risks involved.
- The weather conditions encountered in the final phase of the flight may have aggravated the level of tension in the aircraft cabin to the point of compromising the management of the situation by the pilot, who delegated responsibility for radiotelephony communication to a passenger.
- If one considers that the pilot may have decided to descend below the minimum safe altitude in order to achieve visual conditions, one may suppose that his decision, probably influenced by the experience of the preceding aircraft, was made without adequate evaluation of the risks involved, and without considering the option of flying IFR, in face of the local meteorological conditions. In addition, the pilot’s decision-making process may have been compromised by lack of information on Mount Santo Antonio in the approach chart.
- The primary radar images obtained by Anápolis Control (APP-AN) indicated the presence of thick nebulosity associated with heavy cloud build-ups on the final approach of the VOR procedure. Such meteorological conditions influenced the occurrence, which culminated in the collision of the aircraft with Mount Santo Antônio, independently of the hypotheses raised during the investigation.
- The final approach on the course 320º, instead of 325º, made the aircraft align with the hill with which it collided.
- Mount Santo Antonio, a control obstacle on the final approach in which the collision occurred, was not depicted in the runway 32 VOR procedure approach chart, in discordance with the prescriptions of the CIRTRAF 100-30, a fact that may have contributed to a possible decrease of the situational awareness.

It appears that the loss of directional control after touchdown was caused by the failure of the brake systems. The aircraft had already several technical problems with its brake systems previous to the flight, and maintenance was performed by technicians the day before the accident. For unknown reasons, the problem was resolved but no feedback or troubleshooting was performed on part of the technicians or the crew. The Captain was aware of the problem and took the decision to complete the flight despite the risk the problem may persist or happen again.

Erroneous retraction of the landing gear following three bounces on the runway due to an unstabilized final approach and poor crew resource management.
Contributing factors were:
- Although the descent and landing checklists were followed, the crew did not review stabilized approach criteria or procedures for a possible controlled flight into terrain and did not take into consideration the possibility of any go around procedure
- Several call-outs were non-standard while others were missing
- Descent was continued under visual flight rules, approach was unstabilized and not detected by crew
- Speed was too high on touch down while the power levers were not into idle position
- Lack of corrective action on part of the crew when the aircraft was bouncing
- Loss of situational awareness led to the retraction of the landing gear.

The exact cause of the accident could not be determined.